1. Field of the Invention
The present invention relates to printed wiring board connectors and more particularly to a connector arrangement that utilizes rotating contacts of unique design to provide a zero insertion force type of connector.
2. Background Information
Zero insertion force connectors have been available in the marketplace for well over a decade. Their acceptance by the user community has been sparse and slow largely due to the relative high cost per contact compared to conventional printed circuit board connectors.
Conventional zero insertion force connectors consist of a molded plastic body equipped with two rows of contacts located along both sides of a narrow slot into which a printed circuit board is inserted. At this point no electrical contact is made between the connector contacts and the printed circuit board. Typically, a lever-actuated cam internal to the connector body prevents the contact engagement from occurring. When the lever is then actuated the cam surfaces cause the connector contacts to translate and make electrical contacts with the printed circuit board tabs. This procedure is reversed prior to removing the printed circuit board from the zero insertion force connector.
Connector blocks of this type have been disclosed in U.S. Pat. No. 3,526,869, a connector disclosed therein also requires a large number of parts and is expensive to manufacture in terms of the cost, parts and labor to assemble the parts. Further, of course, as with any zero insertion force connector arrangement such as this, after the daughter board has been inserted it then becomes necessary as a separate step to actuate the cam means to form the electrical connections. Frequently the electrical connections achieved by the conventional zero force type connector do not include the wiping action between the terminal and circuit board pad so that it is possible that there may be an undesirably high contact resistance developed between the terminal and the daughter board. Contact wiping action has long been recognized as a good method of breaking through oxides and other insulating films that occur on contact interfaces. It is also well known that a contact wiping action will also push particulant matter, which can cause electrical opens, away from the point of electrical contact.
Thus, it is obvious from the foregoing that contact wiping action will tend to promote low and stable contact resistance. Another disadvantage to current zero insertion force connectors is their means of actuation. This actuation mechanism is generally located at one end of the connector body where actuation has occurred by rotating a lever through a 90 degree angle or applying a push pull force to a straight rod. In many card files, as utilized in telephone central office switching systems and in some computers, the connectors are located in the backplane at the back of the file and cannot be accessed from the front to perform the necessary zero insertion force actuation sequence. Since cards are inserted and extracted from the front of the card file, the use of zero insertion force connectors at the back of the file is very cumbersome at best. This "volumetric" approach to packaging of printed circuit boards and backplanes however has found wide usage throughout the electronic industry.
A "planar" approach to printed circuit board packaging is being explored and pursued by some manufacturers. Instead of mounting the printed circuit boards perpendicular to the backplane, they are mounted parallel to it. Such an arrangement is also suggested in U.S. Pat. No. 3,701,071 and U.S. Pat. No. 4,273,401. In the present application, the particular implementation proposed is substantially different than that taught in the prior art.